The semiconductor industry uses clean steam for fast silicon oxidation processes. The common process name is "wet oxidation", which is itself subdivided into "field oxidation" (where the thickness of the oxide is greater than one-thousand (1000) .ANG.), and "gate oxidation" (&lt;one-thousand (1000) .ANG.). The clean steam is produced by burning extra-clean hydrogen with extra-clean oxygen in a so-called pyrogenic torch unit.
The usual and safe way to generate pyrogenic steam is by direct injection of hydrogen (H.sub.2) and oxygen (O.sub.2) to the hot (970.degree. C.) oxidation process tube in such a way that the H.sub.2 ignition in the O.sub.2 environment as well as the torch are inside the process tube. This type of system is know by the name "Pyrogenic Internal Torch" (PIT). The main problem experienced in the PIT-type systems is the difficulty in controlling the fluctuation of the oxide thickness due to the temperature imbalance caused by the hydrogen flame. One typically tight specification for oxide thickness uniformity requires a +/-0.5.degree. C. temperature stabilization. This stabilization is strongly interfered at the source zone of the process tube where the torch is situated. Practicably, the silicon wafer load size must be reduced in order to control thickness uniformity, and lessened production capacity has been the result. Additionally, reduced "thermal budgets" for circuits and operation of chambers at less than safe-ignition temperatures for hydrogen have increased demand for H.sub.2 combustion outside the process chamber.
To overcome the problems that are related to the internal heat source, so-called "Pyrogenic External Torch" (PET) systems were developed. The heretofore known PET systems have been constituted by an external, purely-thermal (resistive) ignition element, an H.sub.2 /O.sub.2 quartz injector, a quartz torch chamber, a water-cooled jacket to provide heat transport for the quartz torch chamber, a safety shield and an electronic controller for safety interlocks and operation communications with a main computer controller. The existing PET systems suffer from some major problems including complex seals and feed lines for the water-cooled heat transfer jacket, the requirement for a continuously preheated ignition element (at and above about 760.degree. C.), a long rise time of the heat-up temperature to safe-ignition point by means of the thermal (resistive) ignition element, large flame contours, which demand correspondingly large quartz vessels, a long rise-time to allow such controlled ramping from gas flows at initial torch request to gas flows at practicable gas flow rates as both to prevent flame blow-out and to ensure explosion-free, complete H.sub.2 consumption, and, among others, quartz injector tip erosion due to flame creep-back.